Device and method for extending the lifetime of a battery in a tire pressure sensor

ABSTRACT

A device and method for extending the lifetime of a battery of a tire pressure sensor disposed in a tire are described, in which the battery can be recharged through the valve stem of the tire. The device includes an electrical power source and an electrode adapted to be coupled to the valve stem and supply power from the electrical power source to the valve stem.

FIELD OF THE INVENTION

The present invention generally relates to tire pressure sensors andmore particularly to extending the lifetime of a battery of a tirepressure sensor disposed in a tire.

DISCUSSION OF THE BACKGROUND

Various types of tire pressure sensors have been developed that aresituated within tires of vehicles (see, e.g., U.S. Pat. Nos. 5,540,092and 5,987,980). These tire pressure sensors require electrical power tomonitor and transmit information regarding the current tire pressure fordisplay in the passenger compartment of the vehicle. Typically, the tirepressure sensors are powered by long-life batteries also disposed withinthe tires. The lifetime of these long-life batteries, however, is fiveto ten years, which is less than the life span of many automobiles andtrucks. The effective lifetime of these batteries may be even shorter,because it is not desirable to run the battery down to such an extentthat the tire pressure sensor system fails before the battery isreplaced. Furthermore, replacing a tire pressure sensor battery is alabor-intensive process, involving, e.g., the removal of the tire fromthe wheel.

Accordingly, some tire pressure systems attempt to extend the life ofthe battery by providing a centrifugal switch disposed between the tirepressure sensor and the battery. This centrifugal switch is activatedonly when the tires rotate beyond a certain rate. As a result, thebattery is used for monitoring tire pressure only when the vehicle is inmotion. Another approach to extend the life of the battery is to limitthe transmission of the tire pressure information only to certainconditions, for example, if there is a drop in tire pressure or if thetire pressure information is requested by the driver.

These approaches, however, are difficult to model statistically andtherefore guarantee a reliable battery lifetime that is commensuratewith the life span of the vehicle under a wide range of uses. Forexample, vehicles in interstate trucking are in motion to a much greaterextent than pleasure or commuting vehicles.

Another problem with these approaches is that the usefulness of the tirepressure sensor is curtailed. For example, when the centrifugal switchis used, the tire pressure can only be sensed when the vehicle is inmotion. As another example, when the transmission of tire pressureinformation is limited to certain, rare conditions, the driver of thevehicle cannot be provided with real-time information on the pressure ofthe vehicle's tires.

Therefore, there is a need for extending the life of a battery of a tirepressure sensor and for avoid the necessity of replacing a tire pressuresensor battery. There is also need for making tire pressures useful inmore situations, e.g. when the vehicle is standing still.

SUMMARY OF THE INVENTION

These and other needs are addressed by the present invention, in whichthe tire pressure sensor battery is recharged through the tire valve.For example, a recharging device may be shaped so that the device wouldmate with the tire valve and, when activated, cause a rechargeablebattery in the tire pressure sensor to be recharged. The rechargingdevice can be used by dealers and mechanics at regular service intervalsto ensure that the tire sensor battery is recharged. Advantageously, theeffective life of the battery is extended each time the battery isrecharged and without having to remove the tire. The ability to rechargethe battery through the value stem renders the use of the centrifugalswitch optional, thereby permitting the tire pressure to measured evenif the vehicle is standing still.

Accordingly, one aspect of the present invention pertains to a devicefor charging a battery of a tire pressure sensor within a tire. Thedevice includes an electrical power source and an electrode adapted tobe coupled to a valve stem of the tire and configured to supply powerfrom the electrical power source to the valve stem for charging thebattery. In one embodiment, the device also includes a switch configuredfor selectively supplying power from the electrical power source to theelectrode for charging the battery.

Another aspect relates to a method for charging a battery of a tirepressure sensor disposed in a tire, in which an electrode is applied toa valve stem of the tire and electrical power is supplied to theelectrode for charging the battery. In one embodiment, the electrode isdisposed upon a device that also has a switch. When the switch in afirst position, the electrode can be applied to a valve stem of the tirefor reading an indication of a life of the battery, and when the switchin a second position, the electrode can be applied to a valve stem ofthe tire for supplying electrical power to the electrode for chargingthe battery.

Still another aspect of the present invention pertains to a tirepressure sensor system, comprising a tire pressure sensor, arechargeable battery coupled to the tire pressure sensor, and a valvestem assembly that has a pair of electrodes. The electrodes are coupledto the rechargeable battery for accepting electrical power forrecharging the rechargeable battery. In one implementation, one of theelectrodes is adapted to be coupled to a plunger of a valve stem, andthe other of the electrodes is adapted to be coupled to a threadedconnector of the valve stem. The tire pressure sensor system may alsocomprise a centrifugal switch coupled to the tire pressure sensor, inwhich the electrodes are coupled between the centrifugal switch and therechargeable battery.

To replace a valve stem in yet another aspect of the present invention,an electrode of the valve stem is disconnected from a lead coupled to aterminal of the battery. The valve stem is replaced, and an electrode ofthe replaced valve stem is connected with the lead coupled to a terminalof the battery.

Still other aspects, features, and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a number of particular embodiments and implementations,including the best mode contemplated for carrying out the presentinvention. The present invention is also capable of other and differentembodiments, and its several details can be modified in variousrespects, all without departing from the spirit and scope of the presentinvention. Accordingly, the drawing and description are to be regardedas illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a diagram illustrating an exemplary tire pressure sensorbattery charging device according to an embodiment of the presentinvention;

FIG. 2 is block diagram illustrating the tire pressure sensor batterycharging device of FIG. 1 according to an embodiment of the presentinvention;

FIG. 3 is block diagram illustrating a valve stem adapted for couplingto the tire pressure sensor battery charging device of FIG. 1 accordingto an embodiment of the present invention;

FIG. 4 is flowchart for illustrating a method of charging a battery of atire pressure sensor disposed in a tire using the battery chargingdevice of FIG. 1 and the valve stem of FIG. 3 according to an embodimentof the present invention; and

FIG. 5 is flowchart for illustrating a method removing and replacing thevalve stem of FIG. 3 according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A device and method for extending the lifetime of a battery of a tirepressure sensor disposed in a tire are described. In the followingdescription, for purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It is apparent to one skilled in the art, however, that thepresent invention may be practiced without these specific details orwith an equivalent arrangement. In some instances, well-known structuresand devices are shown in block diagram form in order to avoidunnecessarily obscuring the present invention.

Referring to FIG. 1, a tire pressure sensor battery charging system 100includes a charging device 108 that is coupled to an electric powersource, such as an alternating current-direct current (AC-DC) converter104. In one embodiment, the AC-DC converter 104 receives an AC inputfrom an AC power source 106 by a power line 106 a, such as an 110-voltwall socket, and converts the AC input into a DC output signal for thecharging device 108 via DC signal lines 104 a and 104 b.

In some embodiments, the charging device 108 is also supplied with airfrom an air supply 102 over an air supply hose 102 a. Accordingly, thecharging device 108 can also supply air to a valve stem connectedthereto via air supply input/output 120.

The charging device 108 may include a battery charge display 110, a tirepressure display 112 and a TEST/CHARGE switch 114. The DC signal fromthe DC signal lines 104 a and 104 b can be selectively provided tocorresponding electrodes 118 and 116 of the charging device 108 based ona setting of the TEST/CHARGE switch 114. When the TEST/CHARGE switch 114is set in a CHARGE position 114 b, the DC signal from the signal lines104 a and 104b are provided to the corresponding electrodes 118 and 116.When the TEST/CHARGE switch 114 is placed in a TEST position 114 a, onthe other hand, an indication of the remaining charge on the tirepressure sensor battery is displayed on the battery charge display 110based on a measurement at the electrodes 118 and 116 of an electricalparameter such as voltage or current. The tire pressure of the tireappearing on the air supply nozzle 120 may also be displayed on the tirepressure display 112. The electrodes 118 and 116 are adapted within theair supply nozzle 120 to be electrically and mechanically coupled to avalve stem of tire. The charging device 108 may be shaped similar tothat of existing tire pressure gauges.

In one embodiment, the battery charge display 110 includes an image 110a of a battery and a bar graph 110 b, which indicates a relative amountof life remaining in tire pressure sensor battery in sequence of litbars. The tire pressure display 112 includes a seven-segment display 112a for showing the tire pressure in suitable units, such as pounds persquare inch (PSI). In other embodiments, different representations, e.g.with digital numerals or analog indicia, may be employed.

FIG. 2 is block diagram illustrating one implementation of the tirepressure sensor battery charging device 108 of FIG. 1. In FIG. 2, thecharging device 108 includes a controller 206 coupled to a memory 208,the battery charge display 110, the tire pressure display 112, apressure sensor 202, and a voltmeter 204.

The inputs of the voltage meter 204 may be coupled, for example, to theelectrodes 118 and 116 for measuring a voltage appearing across theelectrodes 118 and 116 when the switch TEST/CHARGE 114 is in the TESTposition 114 a. When the TEST/CHARGE switch 114 is in the CHARGEposition 114 b, on the other hand, the power source from the DC signallines 104 a and 104 b are provided to electrodes 118 and 116. Thevoltage measured by the voltmeter 204 is provided to the controller 206for appropriate processing and, if necessary, conversion and for displayon the battery charge display 110. Alternatively, other kinds of metersmay be used to measure the remaining life of the battery based ameasured electrical parameter, e.g. an ammeter for measuring a currentdrawn from the electrodes 118 and 116.

The pressure sensor 202 measures an air pressure at the air supplynozzle 120. The air pressure measured by the pressure sensor 202 is alsoprovided to the controller 206 for appropriate conversion, if necessary,and for displaying on the tire pressure display 112.

The controller 206 may be implemented in various ways, for example, byone or more microprocessors, digital signal processors, controllers, andmicro-controllers controlled by computer software. The memory 208 mayinclude a combination of one or more of the following: dynamic RAM(DRAM), static RAM (SRAM), synchronous DRAM (SDRAM), read only memory(ROM), programmable ROM (PROM), erasable PROM (EPROM), electricallyerasable PROM (EEPROM), flash memory, etc., for storing information andinstructions to be executed by the controller 206 and temporaryvariables or other intermediate information during the execution ofinstructions by the controller 206. The display devices 112 and 110 mayinclude, for example, liquid crystal displays (LCD), or light-emittingdiode (LED) displays.

FIG. 3 illustrates a tire pressure sensor system 300 that can be coupledto the tire pressure sensor battery charging system 100 of FIG. 1. InFIG. 3, the tire pressure sensor system 300 includes a tire pressuresensor 302, a re-chargeable battery 304, a valve stem 306, and a wheelrim 308. A tire (not shown) can be mounted on the wheel rim 308. Thevalve stem 306 includes a valve stem assembly 310 and a valve stemthreaded connector 318.

In one implementation, the valve stem assembly 310 includes a valve pinor plunger 312, which may serve, for example, as a positive DCelectrode, and a valve stem assembly threaded connector 314, which mayserve, for example, as a negative DC electrode. The valve stem assembly310 can be removed from or replaced in the valve stem 306 via the valvestem assembly threaded connector 314 and corresponding threads in thevalve stem 306. The valve stem assembly threaded connector 314 may beelectrically coupled with the valve stem threaded connector 318. Thevalve pin or plunger 312 is electrically isolated from the valve stemassembly threaded connector 314 and the valve stem threaded connector318. The valve stem assembly threaded connector 314 and the valve stemthreaded connector 318 may be electrically isolated from the wheel rim308.

A voltage lead or wire 312 a, of a first polarity, e.g. positive,connects the valve pin or plunger 312 to a terminal of the rechargeablebattery 304 via removable connectors 312 b and 304 a. Another voltagelead or wire 314 a, of a second polarity, e.g. negative, connects thevalve stem assembly threaded connector 314 to the other terminal of therechargeable battery 304 via removable connectors 314 b and 304 b. Inone embodiment, the connectors 304 a and 304 b are disposed between acentrifugal switch 316 and the rechargeable battery 304 so as to bypassthe centrifugal switch 316 function and allow measurement of a charge ofthe rechargeable battery 304 without the wheel rim 308 being inrotational motion.

Accordingly, the charging device 108 can be both electrically andmechanically coupled to the valve stem 306 via the valve stem threadedconnector 318. For example, the electrode 118 of the charging device 108is electrically and mechanically coupled to the valve pin or plunger312, serving as one electrode of the valve assembly 306. Similarly, theelectrode 116 of the charging device 108 is electrically andmechanically coupled via the valve stem threaded connector 318 to thevalve stem assembly threaded connector 314, serving as the other DCelectrode of the valve assembly 306.

In this way, the battery 304 voltage appears across the electrodes 118and 116 and can be measured when the TEST/CHARGE switch 114 is in theTEST position 114 a. Similarly, the DC voltage from the signal lines 104a and 104 b can be provided to charge or re-charge the battery 304 viathe electrodes 118 and 116 when the TEST/CHARGE switch 114 is in theCHARGE position 114 b. Furthermore, the charging device 108 can alsotest the tire pressure and supply air pressure to the valve stem 306 viathe air supply nozzle 120.

Thus, the systems illustrated in FIGS. 1 and 3 provide the ability tocharge or re-charge the battery 304 that has been partially or fullydepleted. As described above, the battery 304 is electrically coupled tothe valve stem 306, and the valve stem 306 is electrically insulatedfrom the wheel rim 308. The charging device 108 may be incorporated intoa device that is also used to fill tires with air or check tirepressure. The charging device 108 may also incorporate display devices110 and 112 for indicating both air pressure and the battery 304 chargelevel.

FIG. 4 illustrates a process for using the battery charging device 108of FIG. 1 to check the tire pressure and the charge of the battery 304,and, if necessary, to recharge the battery 304. At step 402, a dealer,mechanic, or other user attaches or otherwise applies the batterycharging device 108 to the valve stem 306. The TEST/CHARGE switch 114 isthen moved to the TEST position 114 a (step 404), and, in response, thecharging device 108 measures and displays the battery 304 charge levelat the display 110 for checking purposes (step 406). In oneimplementation, the battery charge level is displayed by lighting anumber of bars on the bar graph 100 b on the battery image 110 acorresponding to the level of charge in the battery 304. In addition,the charging device 108 may also display the tire pressure at display112.

If the battery 304 is to be charged (checked in step 408), theTEST/CHARGE switch 114 is moved to the CHARGE position 114 b (step 410).The charging device 108 is left in contact with the valve stem 306 untilthe battery 304 is charged (step 412). The battery 304 charge may againbe checked (step 406). On the other hand, the process proceeds todecision point 414, which if the tire needs air pressure, air is addedvia the charging device 108 or by another device such as an air hose(step 416), at which point tire pressure may again be checked (step406). This process may be performed by the dealer, for example, at everyservice interval of the vehicle, thereby ensuring that the tire sensorbattery 304 remains charged as long as the vehicle is being regularlymaintained.

FIG. 5 shows the operation of removing and replacing the valve stem of306 of FIG. 3 in accordance with one embodiment of the presentinvention. The dealer or other user dismounts the tire from the wheelrim 308 (step 502). The leads 312 a and 314 a are disconnected from thebattery 304 using the removable connectors 304 a and 304 b (step 504).The valve stem 306 may be removed and replaced (step 506). The leads 312a and 314 a from the replaced valve stem may be connected to the battery304 using the removable connectors 304 a and 304 b (step 508). The tiremay be mounted on the wheel rim 308 (step 510) completing the process.

Although the process of FIG. 5 is described in terms of removing andreplacing the valve stem 306, the process may be performed in anotherembodiment by simply removing the valve stem assembly 310 from the valvestem 306 using the valve stem threaded connector 314. In this case, thevalve stem assembly 310 is actually removed from the wheel 308. Theleads 314 a and 312 a are disconnected from the removable connectors 314b and 312 b of the valve stem threaded connector 314 and the valve pinor plunger 312 of the valve stem assembly 310. The leads 314 aand 312 aare connected to the removable connectors 314 b and 312 b of thethreaded connector 314 and the valve pin or plunger 312 of the new valvestem assembly 310. The new valve stem assembly 310 may be inserted inthe valve stem 306 via the valve stem threaded connector 314 completingthe process.

Accordingly, a device and method for extending the life of a tire sensorbattery is described that avoids problems associated with other attemptsto extend the life of the tire pressure sensor battery. Advantageously,the life of the battery is extended by recharging the batter through thevalve stem, which eliminates the necessity for removing the tire fromthe wheel to physically access the battery. A recharging device can alsobe used, periodically, to check the charge on the battery to determinewhether or not the battery may need to be replaced or simply re-charged.The battery charge can be tested in conjunction with another serviceitem for the vehicle, so that testing of the battery charge need not beforgotten. For example, the battery charge is tested in conjunction withthe checking of the tire pressure at a dealership, as checking the tirepressure may be done frequently.

While the present invention has been described in connection with anumber of embodiments and implementations, the present invention is notso limited but rather covers various modifications and equivalentarrangements, which fall within the purview of the appended claims.

What is claimed is:
 1. A device for charging a battery of a tirepressure sensor within a tire, comprising: an electrical power source;and an electrode adapted to be coupled to a valve stem of the tire andconfigured to supply power from the electrical power source to the valvestem for charging the battery.
 2. A device for charging a battery of atire pressure sensor within a tire, comprising: an electrical powersource; an electrode adapted to be coupled to a valve stem of the tire;and a switch configured for selectively supplying power from theelectrical power source to the electrode for charging the battery.
 3. Adevice according to claim 2, further comprising: a meter; wherein theswitch is further configured for selectively coupling the electrode tothe meter for measuring an electrical parameter at the electrode.
 4. Adevice according to claim 3, further comprising: a display deviceconfigured for indicating a life of the battery based on a measurementof the electrical parameter.
 5. A device according to claim 3, wherein:the meter includes a voltmeter for measuring a potential at theelectrode or an ammeter for measuring a current drawn from theelectrode.
 6. A device according to claim 2, further comprising: an airsupply nozzle adapted to supply air to the valve stem.
 7. The deviceaccording to claim 6, further comprising: an air pressure sensor adaptedto measure air pressure at the air supply nozzle; and a display deviceindicating a measured air pressure.
 8. A device for charging a batteryof a tire pressure sensor within a tire, comprising: an electrical powersource; a nozzle having an electrode adapted to be coupled to a valvestem of the tire; a meter; a switch configured for selectively supplyingpower from the electrical power source to the electrode for charging thebattery or coupling the meter to the electrode for measuring anelectrical parameter; and a display for indicating a life of the batterybased on a measurement of the electrical parameter.
 9. A deviceaccording to claim 8, further comprising: an air supply for supply airto a valve stem of a tire via the nozzle.
 10. A method for charging abattery of a tire pressure sensor disposed in a tire, comprising:applying an electrode to a valve stem of the tire; and supplyingelectrical power to the electrode for charging the battery.
 11. A methodfor maintaining a battery of a tire pressure sensor disposed in a tire,using a device having a switch and an electrode, comprising: with theswitch in a first position, performing the steps of: applying theelectrode to a valve stem of the tire; and reading an indication of alife of the battery; and with the switch in a second position,performing the steps of: applying the electrode to the valve stem; andsupplying electrical power the electrode for charging the battery.
 12. Amethod according to claim 11, further comprising: applying an air supplynozzle containing the electrode to the value stem; and supplying air tothe valve stem of the tire.
 13. A tire pressure sensor system,comprising: a tire pressure sensor; a rechargeable battery coupled tothe tire pressure sensor; and a valve stem assembly including a pair ofelectrodes; said electrodes coupled to the rechargeable battery foraccepting electrical power for recharging the rechargeable battery. 14.A tire pressure sensor system according to claim 13, wherein: one of theelectrodes is adapted to be coupled to a plunger of a valve stem, andthe other of the electrodes is adapted to be coupled to a threadedconnector of the valve stem.
 15. A tire pressure sensor system accordingto claim 13, further comprising: a centrifugal switch coupled to thetire pressure sensor.
 16. A tire pressure sensor system according toclaim 15, wherein: the electrodes are coupled between the centrifugalswitch and the rechargeable battery.
 17. The valve stem assemblyaccording to claim 13, wherein: the valve stem assembly is assembledinto a valve stem.